Surfacing apparatus



Aug. 20, 1929. w, MALL 1,725,361

SURFACING APPARATUS Filed Nov. 3, 1928 I N VEN TOR.

A TTORNE Patented Aug. 20, 1929.

UNITED STATES 1,725,361 PATENT OFFICE LBTHUB w. .MALL, OF CHICAGO, ILLINOIS, ASSIGNOB TO THE BTRLTMORE COMPANY, OF CLEVELAND, OHIO, A CORPORATION O1 OHIO.

BUBFACING Arramvrvs.

I The present invention, relating, as indicated, to surfacing apparatus is more part cularly directed to an improved supporting pad for use in surfacing apparatus of the type now so commonly used for grlnding, polishing, bufieting and similarly treating surfaces such as panels of wood, metal and other material, and such articles as castings, automobile bodies, fenders, hoods and the like. The apparatus commonly employed for this purpose consists of a frame or casing provided with handles for an operator and with a projecting shaft, on the end of which is mounted a supporting pad, against which is removably secured a surfacing disk, usually constructed of abrasive adhesively "secured to a suitable backing of paper, cloth or some combination of the two.- The shaft on which the pad and disk are carried is operated through gearing journaled in the 1 frame or casing and then-by a flexible shaft extending to a suitable source of power, al-' though in many cases the operating shaft which carries the pad and disk are operated directly from a self-contained air. or electric motor mounted in the frame or casing.

The present invention is directed to a new and improved pad to be used in machines of the above construction and for the puroses, some of which are referred to above.

he principal object of the invention is the provision of a simple and inexpensive pad for the purpose described and one which has a more universalapplication and usefulness than the more specialized and expensive pads which have heretofore been employed, but which have been better adapted to some individual type of surfacing operation thanto general operations involving a consider-- able range of operations. I

To the accomplishment of the foregoing and related ends, said invention, then, consists of. the means hereinafter fully described and particularly pointed out in the claims; the annexed drawing and the following descri tion setting forth in detail certain mec anism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may'beused.

In said annexed drawing Fig. 1 is a side elevation partially in section of an apparatus of the character described carrying my improved pad; Fig. 2'

is a side elevation of the same showing the service and the capacit method of operation in surfacing a curved which may extend to any suitable source of power, such for example as an electric or other motor mounted on any suitable support. In the casing 1 are provided suitable right-angle gearing for operating an extending shaft 4 from the flexible shaft carried in the handle 3, the shaft 4 being provided with a reduced and threaded end 5, which is hollow and is formed with internal threading 6' for the purpose presently to be described.

Removably mounted on the threaded end 5 of the shaft 4 is a supporting pad for the surfacing disks which are to be employed in the use of the machine. supporting pad is shown in Fig. 1 and consists of a relatively solid or rigid support 10 provided with a hollow central portion which is internally threaded to engageover the other end of the shaft. Secured to the lower face of this support 10 is a'pad proper of peculiar characteristics. T is ad 11 consists of a circular disk formed 0 slightly compressible and flexible material which is con-' structed, however, to resist fiexure out of its normal plane, although capable of such flexing under strong lateral pressure. Other characteristics which are required in such a device, and which are found in the present construction are extreme toughness to prevent injury to the pad even under severe to compress throughout its lower ortion, that is the portion against which t e surfacing engages, to compensate for slight irregularities in the surfacebeing operated upon before there is any real lateralflexure in the supporting pad proper. The supportingpad compressible material, such for example as rubber, reinforced in its upper or rear ort y 2 numbers! shee s 12 of strong i s-formed of a tough,

ric, which give the pad a. very considerable strength and which. so stiffen it that while capable of deflection out of its normal plane it still resists such deflection, except under heavy pressure. The reinforced fabric is disposed chiefly in the upper portion of the pad, leaving the lower portion 13 unremforced and hence more readily capable of compression to compensate for the. irregularities of the surface and to cushion the shocks otherwise directly transmitted from such irregularities to the abrasive disk. This pad 11 is removably secured to the support 10 by means of studs 14 disposed in suitable recesses 15 and engaged by washers or nuts '16 which aresunk into the lower surface of the inner portion of the pad.

The support 10 is not merely a hub for receiving the pad, but is also a support which affects the entire operation and flexing of the pad in use. The support 10 extends from one-third to one-half the distance from the center to the periphery of the pad 11, and in pads of small size for light work, extends over an even greater portion of the entire area of the entire pad proper.

An abrasive disk of considerable strength may be mounted against the lower or supported surface of the pad in the manner shown in Fig. 1. This disk 20, which is substantially coextensive in size with the pad, is provided with a central opening and is applied by being superimposed against the lower surface of the pad and there fastened in position by means of a. nut 21 providedwith an extending flange 22 and with a central threaded hub 23, which engages in the internal threading of the shaft 6. By insertin and turning down this nut the abrasive dis is securely located in position against the pad and is held there by the frictional pressure exerted between the pad and both the flange 22 and the tapered portion 24.- of the hub of the nut.

In small shops where small surfacing machines of this general character are now employed as practically a standard tool there are a great variety of operations which it is desired to carry out, particularly on such articles as automobile bodies. These operations include the removal of small rust spots, paint, dirt, grease and the like, the smoothing down of surface spots on the body for repainting or refinishing, the grinding down of welds and the like, and, due to the nature of these bodies, ithas been extremely diiiicult to operate on the various types of surfaces which are found, which are both convex and concave with a single machine, or rather with a single appliance or final tool on a machine of this general character. In the past it has been necessary, for example, to work on the large relatively flat or slight- 1y curved surfaces of a body with a large pad and abrasive disk and to then substitute for this tool a solid or cup wheel, a pneumatic wheel, or a long narrow cone to carry on other operations, such as the smoothing down of inwardly curved surfaces, touching up the corners of window openings and the like. This substitution required the user to purchase-a variety of different tools and to lose time whenever a shift was made from one operation to another. The present pad is designed to carry out substantially all of these operations and is so constructed that almost any type of surface can be satisfactorily operated upon with an abrasive disk.

One illustration of the work done by such a tool is shown in Fig. 2. The device is there shown as operating against a curved lower surface of a fender 30 of an automobile body and the pad 11 is shown as bent a considerable distance out of its normal plane to bring the abrasive fully against this curved portion of the fender. In Fig. 3 a similar view is shown illustrating the adaptability of the pad 11 to a surface 31 of still greater curvature, while in Fig. 4 I have shown substantially the maximum deflection at which the pad will operate satisfactorily. This Jill be seen to involve a very considerable bend in the pad, the character of which is influenced and affected by the solid supporting hub 10.

It is of particular importance that the pad be constructed to permit of these sharp flexures under heavy pressures and I accomplish this by the disposition of the reinforcing material in the rearward or upper portion of the pad, leaving the lower portion of pure flexible material, such as rubber, which permits this portion to stretch and to increase its surface length as required when the body is bent into the curvaturesthat have been shown. This bending would be very seriously affected if the reinforcing ma terial were carried throughout the top of the pad and lay close to the outer surface which is in tension during the flexure of the pad through large angles.

It is also important that that portion of the abrasive disk whi ch has the greater speed and cutting effect, namely, the radially outer portion, be forced against the work, and this is accomplished through the toughness and resistance to flexure of the entire pad and the supporting eflect of the large solid support 10, which prevents the pad proper from bending from its center, but forces it to bend from a point beyond the circumference of the support. In this way the radially outer against the work the speed of operation is necessarily reduced, which is not the case when only the radially outer portion of the disk is brought into action.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed,

rovided the means stated by any 'of the ollowing claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention 1. In a surfacing device of the character described, the combination of a circular element for supporting an abrasive disk, said element being constructed to permit stretching on its outer surface and having means restraining stretching in its rear portion and capable of supporting said disk in substantially its normal plane under normal lateral operating pressure, and also capable of yielding out of its normal plane under abnormal operating pressure to allow a disk supported thereby to engage and conform to concave surfaces, a rigid disk support disposed centrally against one side of said element, said support extending outwardly from one-third to one-half the distance from the center to ment for supporting an abrasive disk formed of a tough compressible material having reinforcement only in its rear portion and 'capable of su porting said disk in substantially its norma plane under normal lateral operating pressure, and also capable of yielding out of its normal plane under abnormal operating pressure to allow a disk supported thereby to engage and conform to concave surfaces, a supportin disk disposed centrally against one side 0 said element, said support being substantially rigid and extending outwardly from one-third to onehalf the distance from the center to the edge of said element, and an abrasive disk disposed against the other side of said element, said last disk being attached at its center portion only to said element.

Signed by me, this 1st day of November,

ARTHUR W. MALL. 

